Work

Validation of Ps‐P Tomography for Obtaining 3D Crustal VP/VS With Small‐N Data Sets: An Application to the Mount St. Helens Magmatic System

Year: 2024

Type: article

Abstract: The high sensitivity of VP/VS to the presence of melt makes images of VP/VS structure particularly useful in magmatic systems, but detailed three‐dimensional models of VP/VS structure in magmatic systems are often restricted to the upper crust where there is a concentration of seismic sources used for imaging. Ps‐P tomography is a new technique that has been used to image three‐dimensional crustal‐scale variations in VP/VS in regions with limited seismic instrumentation. We apply the Ps‐P tomography technique to a well‐constrained, independently imaged magmatic setting, Mount St. Helens, to outline the efficacy and limitations of this imaging approach. Our Ps‐P tomography model reveals previously imaged high VP/VS upper crustal magma reservoirs beneath active volcanic systems at Mount St. Helens, Mount Adams and the Indian Heaven Volcanic Field and low VP/VS anomalies associated with crystallized plutons. Our model also provides new VP/VS constraints in the lower crust that reveal a high VP/VS anomaly connecting the Mount St. Helens and Mount Adams reservoirs and a low VP/VS anomaly associated with lower crustal cumulates or mafic accreted terranes. Decimation tests further show that first order VP/VS structure is recoverable using as few as four recording seismometers. These images resemble those of independent, higher resolution images from traditional techniques, highlighting the utility of Ps‐P tomography for imaging three‐dimensional variations of VP/VS throughout the crust, including in data‐poor settings or with arrays not designed for structural seismic investigations, such as many volcano monitoring networks.

Source: Journal of Geophysical Research Solid Earth

DOI: 10.1029/2024jb029642

Authors: Daniel Evan Portner, Jonathan R. Delph, Eric Kiser, Geoffrey A. Abers, Alan Levander, Guanning Pang